What is the thing that goes under the master cylinder that connects all 4 brake calipers to the brake master cylinder called and what would you suggest to do if i lost mine

It's called a brake proportioning (aka prop) valve. Sr5 and gts are different. I believe they're all discontinued from toyota, and I don't think there are any application specific aftermarket replacements. You'll probably have to scour tye classifieds for a used unit, or adapt an aftermarket adjustable unit like this: http://www.jegs.com/i/Wilwood/950/260-1 ... AslG8P8HAQ

Deuce Cam wrote:It's called a brake proportioning (aka prop) valve. Sr5 and gts are different. I believe they're all discontinued from toyota, and I don't think there are any application specific aftermarket replacements. You'll probably have to scour tye classifieds for a used unit, or adapt an aftermarket adjustable unit like this: http://www.jegs.com/i/Wilwood/950/260-1 ... AslG8P8HAQ

Thanks. I found one used on ebay for 57.00 but I don't know if its for gts or sr5. I'll just get the adjustable unit.

From personal experience, I've had no problems with sr5/gts combos of prop valves and rear ends. I've done 22 gtsr5 of all kind.